Artificial insemination is commonly used to increase pregnancy rates and overcome fertility problems for humans and is also often used to breed animals for increasing genetic gain by using semen from males with desirable genetics. While many methods and devices are known for achieving artificial insemination, it is believed that many of the known techniques are inconvenient, expensive and have been less than successful in achieving higher pregnancy rates.
In humans artificial insemination is often accomplished by using a pericervical technique in which a cervical cap is filled with 0.5 to 1.0 ml. of semen and placed over the patient's cervix which causes the semen to diffuse and spread evenly over the inside of the cap and over the cervix. This technique is problematic in that only a small portion of the semen is exposed directly to the cervical Os and the majority of the semen expires where it is trapped between the cervix and the cap. Another technique is intrauterine insemination in which semen is directly deposited into the uterus using a pipette and the hostile environment of the cervical canal and mucus is bypassed. This technique is relatively difficult to accomplish, is time-consuming, and requires highly trained personnel to administer the treatment as it involves intrauterine manipulation which has inherent health risks including the potential of causing infection. In addition to its cost and complexity, it has also been found that intrauterine insemination generally does not offer any significant advantage in pregnancy results as compared to cervical insemination. Friedman A, Haas S, Kredenster J, et al., 1989 Int. J. Fertil. 34:199; Nachgigall R. D., Faure N, Glass R. J., 1979 N. Engl. J. Med. 32:141; Peters A. J., Hecht B, Wents A. L., et al., 1993 Fertil. Steril. 59:121.
In animals artificial insemination is often accomplished by vaginal insemination, cervical insemination or intrauterine insemination, which all suffer from their own complexities and problems. In particular, vaginal insemination involves depositing a sample or bolus of semen into the anterior vagina and this technique generally does not increase pregnancy rates beyond that associated with natural insemination. Cervical insemination is probably the most successful method of inseminating animals and it involves introducing semen into the cervical canal or uterus with a pipette which is inserted as deep as possible into the cervix without using force. While this method has been effective for artificially inseminating dairy cattle, it is impractical for use with many types of animals. For example, the cervical canal of sheep is closed by reciprocal folds and depressions of the mucus membrane which prevent insertion of a pipette into the cervix to any depth. For such animals, intrauterine insemination is an option but that technique is performed laparoscopically under anesthesia which requires trained personnel, is expensive and time consuming, and has a potential risk to the animal. Despite the complexities and expense associated with that technique, it is growing in popularity for inseminating sheep as there is a strong desire to take advantage of the genetic gain offered by artificial insemination which has been successfully utilized in other breeding programs such as for dairy cattle.
A recent study has demonstrated that a significantly higher rate of pregnancy can be achieved by intrauterine insemination which is administered over a period of time, such as three hours, than when insemination is performed by simply introducing a bolus of sperm into the uterus. Muharib N. S., Gadir A. A., Shaw R. W., 1992 Human Reprod. 7:227. While it has been recognized that slow introduction of semen into the uterus enhances the rate of pregnancy, the technique used in the noted study is inconvenient and expensive for use with humans and is impractical for use with animals. In particular, the technique involved having the patient lie supine on a bed for a period of hours and a plastic tube was introduced into the uterine cavity after exposing the cervix with a bivalve speculum. The speculum was then removed and the tube was attached to a slow-release auto-syringe with an auto-syringe driver placed on the bed beside the patient. The study notes that many of the patients were initially apprehensive towards use of an intrauterine catheter. The study proposes that the disadvantages of the technique could be lessened by using a self-retaining intrauterine catheter in which the pump or driver is strapped to the patient's leg. However, the proposed system is still complex, results in limited patient mobility, and is unrealistic as an option for breeding animals.
Other attempts have been made in the prior art to provide a time-release insemination device such as exemplified in Dickinson U.S. Pat. No. 3,811,443. Dickinson discloses a device having a complicated anchoring assembly for securing the device in a vaginal canal which presents problems of patient comfort and acceptance. The means for expelling semen from the device into the cervical canal also present problems. One embodiment discloses the use of seeds which emit carbon dioxide to develop a pressure in the device to discharge the semen. However, it is believed that such a device would not develop a sufficient pressure to overcome the resistant forces of the mucus in the cervical canal for successful delivery of the semen. Dickinson also proposes using dry ice (solid carbon dioxide) to expel the semen but is believed that the expense and complications encountered with handling dry ice renders such a construction impractical for widespread use. The device is also complicated with respect to filling the device with semen and loading the expansion chamber.
An important aspect of this invention therefore lies in providing an insemination device which administers semen to the cervical canal or uterus over a period of hours and has a simple and efficient construction that may be easily used with humans or for breeding animals. Such results are achieved by providing a device with a cervical cap which conforms and adheres to the patient's cervix and which includes an elongated nipple for insertion into the cervix or uterus for intracervical or intrauterine insemination. A self-contained time-release mechanism is provided in communication with the nipple for discharging semen through the nipple and into the cervix or uterus over a period of hours. The mechanism includes a tubular member which defines a semen chamber in communication with the nipple and an expansion chamber which is separated from the semen chamber by a plunger. The expansion chamber is filled with a water-swellable material and is attached to a resilient, collapsible reservoir which supplies fluid to the water-swellable material. In use, the device is inserted into the vaginal canal of the patient and the cervical cap fits snugly over the patient's cervix to retain the device in position. Over a period of hours, the water-swellable material in the expansion chamber draws or absorbs fluid from the reservoir and expands so that the plunger is urged towards the cervix and causes a slow time-release discharge of semen through the nipple and into the cervix or uterus.
In brief, the time-release insemination device of this invention comprises a dome-shaped cervical cap adapted to conform and adhere to a cervix and having a peak portion at one end and a generally circular periphery at the other end. An elongated tubular nipple which defines a passageway extends from the peak portion of the cap in a perpendicular direction towards the circular periphery for insertion into the cervical canal or uterus. For animals having a generally unobstructed cervical canal, the nipple preferably has a distal end which extends beyond the circular periphery of the cap to discharge semen into the middle or posterior end of the cervical canal or uterus so that the hostile environment of the cervical mucus is bypassed. For animals having a obstructed cervical canal, the nipple preferably has a distal end which does not project beyond the circular periphery of the cap so the nipple is positioned directly adjacent to the cervical Os. The time-release mechanism includes an elongated tubular member that defines a semen chamber which is in fluid communication with the nipple's passageway and defines an expansion chamber which is separated from the semen chamber by a plunger slidably mounted therein. Reservoir means are provided in fluid communication with the expansion chamber for providing a quantity of fluid thereto. Within the expansion chamber, expansion means are disposed for absorbing fluid from the reservoir means and expanding so that the plunger is urged towards the cervical cap to cause discharge of semen from the semen chamber through the passageway of the nipple and into the cervical canal or uterus.
The device preferably includes sealable aperture means which are in communication with the expansion chamber and the reservoir means for allowing withdrawal or introduction of fluids therefrom or thereto. Such sealable aperture means may take the form of known self-sealing elements or injection sites commonly used in the medical industry. The reservoir means is preferably constructed of a resilient balloon-shape reservoir which defines an interior volume and is operable between a collapsed state in which the volume is evacuated and an expanded state in which the volume is filled with fluid. Such a construction facilitates filling the semen chamber with semen and filling the reservoir with fluid without causing premature discharge of semen from the device. More specifically, withdrawal of fluid through the self-sealing aperture evacuates and collapses the reservoir and draws the plunger towards the distal end of the tubular member to create a negative pressure in the semen chamber and passageway of the nipple for drawing semen into the device. Once the semen chamber is filled and the reservoir is collapsed, fluids such as water can be introduced through the self-sealing aperture to fill the collapsed reservoir back to an expanded state without the fluid significantly entering the expansion chamber and causing premature movement of the plunger or unnecessary discharge of semen.
In an alternate construction, the sealable aperture means may take the form of a self-sealing element or injection site as previously described and a unidirectional valve also provided in communication with the reservoir means and the expansion chamber. In such a construction, the reservoir means may be collapsed by squeezing the reservoir between a user's fingers so that the air or fluid in the reservoir is evacuated through the unidirectional valve. Thereafter, the distal end of the nipple is inserted into a quantity of semen and the collapsed, resilient reservoir is released so that it resumes its expanded state and creates a vacuum which draws the plunger towards the distal end of the tubular member, thereby drawing semen into the nipple. Once the semen chamber is filled and the reservoir is expanded, fluid such as water is introduced through the self-sealing element to fill the reservoir while the air already in the reservoir is allowed to escape through the unidirectional valve. The unidirectional valve is preferably positioned on the tubular member adjacent to the expansion chamber.
The expansion means preferably take the form of a water-swellable material and alginates or seaweed have been found to be particularly suitable of this purpose. Laminaria seaweed is believed to be preferable as it slowly expands over a period of hours when exposed to water. However, other suitable hydrocholoids which provide a slow release of semen through the device may also be effective. Preferably, the device releases the semen over a period of at least 3 hours, preferably 6-8 hours.
The cervical cap may also be provided with release means for minimizing surface adhesion between the cervical cap and cervix, and the release means may take the form of a plurality of holes formed in the cervical cap which reduce its surface area. The reduction in surface adhesion between the cervical cap and the cervix facilitates removal of the device after the semen has been deposited. Conversely, it may be desirable in some applications to provide the cervical cap with improved retention capabilities, and projection means may be provided on the nipple for engaging the side walls of the cervical canal. Such projection means may take the form of a spirally-extending rib. It is also contemplated that in some embodiments it would be useful to form the cervical cap of a biodegradable or water-soluble material which, after full release of the semen, would sufficiently degrade or dissolve such that it would automatically disengage from the cervix and would be naturally expelled by the animal.
Other features, objects and advantages of the invention will become apparant from the drawings and specifications.